car battery & system problems,plausible?

Hello again, This last 2 months my vw t4,7da,swb,pet,2.0lt has been worked on in the garage to find why it won't start. Parts of the ignition were replaced and briefly ran again until it stopped agawork and became the reason it restarted but with added mistakes of compensating for fixed parts therefore adjustments needed.The reason for its non-start is debated in various ways and this one is A most likely. A new battery is next to go in because the old one is old. But this only means it can't give enough power. Or so I think.......? Q. Is this old battery likely to have caused damage or create its powerless current in a deformative way system wide, enough to confuse the electrics into a start/stop state? Clearly it would hold a less powerful command over the electrical system but fluctuating currents in it might hold a devastation unseen. A typical trend would be in idle the van just shuts off and no spark is given to the spark plugs. But when tests are done they seem operable and most associated parts with the ignition are replaced, eliminating err. Q. Could it be capable of that. It has a digifant II electronic injection and immobilizer which all rely on accuracy(and there are many components relying) so every new part increases the likely hood that it will work, but it seems to be getting no where ;WITH information from the ecu(computer) and hands on tests. It all is underlined by the unknown area which causes the problem and not much seems highlighted with broken parts. So it may be from such instances however trivia     I don't mean that it can provide the actual sole reason for all of the problem, rather could the fluctuation of energy vary wildly enough to support a voltage or current 'lightning strike' because internally it is suffering the same. My electronic mind is limited. Sorry.

Battery, alternator, low power = battery. Fluctuating power = alternator. Immobiliser, if faulty well not let you start cannot cut out the engine once running. Also possible, O2 sensor. That will kill the idle once warm.

Geez those Aussie speak funny... As per Howie II. Alternators & batteries should be easy to check. If 'garage' means a mechanic, then she/he should have a DMM (multimeter) and know how to do basic checks. (I know there are some electrically hopeless mechanics out there, but geez man, even in ye olde days one usually had to eliminate electrics as a possible problem. These days it usually a case of send the vehicle to an auto electrician BEFORE sensing it to a mechanic - unless the mechanic has good electrical and sensor testing skills.) The alternator should be charging above 14V except perhaps at idle or low speed with heavy loading (after cranking with lights & wipers etc on).    A bad battery will dip significantly during cranking - eg, below 9V or 8V. A fully charged battery should be ~12.7V after it has dissipated surface charge after charging (that can take up to ~24 hours). Even simple tests like headlight brightness at idle versus revving can confirm electrical issues.

Blimey mate oi couldn't understand what you geezers from the sarfern emisphere are on.

Thanks for the assistance, I used a multimeter to find that the distributors NEW hall sender isn't working. I can't understand what causes the electrical components to stop working or become broken.     As I understand the voltage, if different THEN things become broken but the other ways I have no knowledge of. As you say alternator would have an influence, but these parts don't work any more. Ignition switch,ignition,ignition transformer coil,distributor hall sender,spark plugs, rotor and cap,idle regulator and battery(Wednesday). What could be the reason. The batterys MORE responsible than the alternator or the whole vehical isn't earthed. I've just never heard of electrical failure without component damage or incorrect power sources. That's OK if you don't understand the situations difficult anyway. Thankyou for your help anyway.

To be honest I've never come across a petrol T series, only diesel. Having said that they (VAG cars) are notorious for ECU and component such as coil pack failures. A Hall effect switch with no moving parts? Though having said that I had a cam position sensor fail last year, also a hall effect switch.

Ah - I missed the VAG (VW) part. (2 weeks ago there was a car fire outside my work - I had left early. I asked if it was a continental (ie, Euro) car. Yep - sure enough - a BMW. Geez - what did I know - other than TC Cortinas and Jag XJ-6s tend to be rare these days... ) The only thing that should be causing successive electrical failures is overvoltage (ie, alternator goes too high; usually above 16V) else bad connections that cause intermittents, hence thermal fatigue & component failures. (Repetitive bulb failures are usually caused by intermittents. I don't know why people keep blaming "shorts"!) Halls are less reliable than reluctors but they should be reasonably reliable. As I recall, Siemens HKZ series "vane" Hall modules as widely used for distributors operate to over 20V. Car & their components can have a design life - especially these days. (The old rule was if you owned a Euro (including UK) car, get rid of it once it starts causing trouble.) First I'd suggest disconnecting and reconnecting all connectors; rotating same sized fuses; & cleaning battery terminals. IMO that fixes over 90% of electrical problems. Also remove & refit the GND connections from battery- to engine & body/chassis (clean surfaces if they look contaminated; ditto for any fuses or connectors). Also ensure no engine or engine bay overheating. POST EDIT- and engine or other vibration. After that I'd suggest taking it to an auto electrician. They should be able to scope (oscilloscope) the DC supply to check for excessive spikes (eg, from fan motors or due to aged batteries that are less at effective absorbing transients).    Mechanics are usually not the solution. Even if they know how to test a fuel pump or use a DMM, they probably don't have scopes etc. Mechanics can however prove very good at blowing ECUs, or replacing every ECU sensor trying to find some running fault. That reminds me - a special thanks to whoever replaced all ECU components in that 1988 Astra at Pinch A Part Kilsyth; I now have a Delco setup for my old engines complete with new sensors - even a brand new HEI module! (I don't use those crappy multi-piece reluctors as used in N13s & Camiras & VN Commodores so its brand new dizzy was otherwise a total waste.)

....over voltage from the alternator, I read somewhere there's a place on it ,symbolized with an "A" that is prone for errors. I'll look over it. This is my first van/car in over 15years and it was a nice change to be able to get into the vehical via the vagcom, using its capabilities with the injection was a fun component. Its just silent whilst everything isn't working..

old battery multimeter 13.4 VOLTS       new battery 12.8 volts So what's damaged....where should I look for that(eg burned wires, parts that are under par with 13v useage) . I left the charger on and off for three days to get right up to full power and its hidden defect reveals itself, what did you say...thermal fatigue & component failure, intermittents....to what extent will this penetrate the system, HAS penetrated? Already the new $130 hall sender won't supply the spark. Replaced no30 relay and will have to get the components again! Test and trace for only weaker parts, which will fall? Which ones would/could sustain the overvoltage if any, it could save some money in replacement parts. The alternator needs a test output value could you enlighten me please.

The old battery must have been after a charge with residual surface charge. A 12V lead acid battery cannot be more than 12.7V (with few exceptions). Car components will handle 14V since normal long-term charging voltages are usually up to 14.4V. The usual spec for (automotive) 12V equipment is up to 16V. And fuses should blow before any wiring melts - that's what they are there for. There are some exceptions like the heavy starter motor cable; ignition (coil) on older vehicles, and any unfused wire leading to a fuse.    Hall senders (ie, sensors or modules) only supply a signal to the ECU ot IgCoil ignitor. (Reluctors are the only sensor modules with inbuilt ignitors tho some are sensor only that feed ECUs or external ignitors etc.) Have you checked the IgCoil? The alternator should charge at up to 14.4V though some may exceed that after initial startup. Modern 12V vehicles are usually set to 14.4V else 14.2V. 13.8V was the old set point but that is too low for modern batteries and prolonged battery life. Alternators may be lower than 14V etc at idle or low RPM with heavy loading - eg. lights & wipers - but should return to ~14V at normal RPM. Some newer alternators will drop to ~mid 13V when the battery is fully charged. Some assume full charge after some delay (say 10 - 60 minutes) or when the alternator reaches a certain temperature. Alternators often vary output voltage with temperature since bater charge voltages vary with temperature. I mention the above exceptions in case the typical 14.2V - 14.4V is not observed so you realise it might not be a fault.